Lubricating Composition Containing Ashfree Antiwear Agent Based on Hydroxypolycarboxylic Acid Derivative and a Molybdenum Compound

ABSTRACT

The invention provides a lubricating composition containing an oil of lubricating viscosity, an oil soluble molybdenum compound, and an ashless antiwear agent. The invention further provides for a new antioxidant. The lubricating composition is suitable for lubricating an internal combustion engine.

FIELD OF INVENTION

The invention provides a lubricating composition containing an oil oflubricating viscosity, an oil soluble molybdenum compound, and anashless antiwear agent. The invention further provides for a newantioxidant. The lubricating composition is suitable for lubricating aninternal combustion engine.

BACKGROUND OF THE INVENTION

Engine manufacturers have focused on improving engine design in order toimprove fuel economy and efficiency (typically, based on FederalCorporate Average Fuel Economy (CAFE) standards). Whilst improvements inengine design and operation have contributed, improved formulation ofengine oil lubricant may also improve fuel economy and efficiency.Lubricants function to reduce and disperse engine deposits whichaccumulate when the engines are running. They also serve to reduce thefriction between sliding moving parts (typically metallic or ceramic)that are in contact.

It is well known for lubricating oils to contain a number of additives(including antiwear agents, antioxidants, dispersants, detergents etc.)used to protect the mechanical devices such as internal combustionengines from wear, oxidation, soot deposits and acidity build up. Acommon antiwear additive for engine lubricating oils is zincdialkyldithiophosphate (ZDDP). It is believed that ZDDP antiwearadditives protect the engine by forming a protective film on metalsurfaces. ZDDP is also believed to have a detrimental impact on fueleconomy and efficiency. Consequently, engine lubricants also containfriction modifier to obviate the detrimental impact of ZDDP on fueleconomy and efficiency. Both ZDDP and friction modifier function byadsorption on sliding surfaces, and each may interfere with each other'srespective functions.

Further, engine lubricants containing phosphorus compounds and sulphurhave been shown to contribute in part to particulate emissions, andemissions of other pollutants. In addition, sulphur and phosphorus tendto poison the catalysts used in catalytic converters, resulting in areduction in performance of said catalysts.

With increasing control of emissions (often associated with contributingto NO_(x) formation, SO_(x) formation, formation of sulphated ash andreducing the efficiency of after-treatment catalytic converters) thereis a desire towards reduced amounts of sulphur, phosphorus and sulphatedash in engine oils. However, reducing the levels of antiwear additivessuch as ZDDP, is likely to increase wear and result in other detrimentalperformance of an engine.

In addition, as technology develops, components of an engine are exposedto more severe operating conditions. Operating conditions may includehigher power density engines, use of turbo chargers, use of alternativefuels and the like. Under many severe operating conditions, oxidation oflubricant and components occurs more readily. Thus there is a need toreduce oxidation, that in turn may also increase equipment longevity, orreliability.

International Publication WO 2005/087904 discloses a lubricantcomposition containing at least one hydroxycarboxylic acid ester orhydroxy polycarboxylic acid. The lubricant composition disclosed mayalso contain zinc dihydrocarbyldithiophosphates, or otherphosphorous-containing additives such as trilauryl phosphate ortriphenylphosphorothionate. The lubricant composition has anti-wear oranti-fatigue properties.

International Publication WO 2006/044411 discloses a low-sulphur,low-phosphorus, low-ash lubricant composition suitable for lubricatingan internal combustion engine, containing a tartrate ester, or amidehaving 1 to 150 carbon atoms per ester of amide group.

U.S. Pat. No. 5,338,470 discloses alkylated citric acid derivativesobtained as a reaction product of citric acid and an alkyl alcohol oramine. The alkylated citric acid derivative is effective as an antiwearagent and friction modifier.

U.S. Pat. No. 4,237,022 discloses tartrimides useful as additives inlubricants and fuels for effective reduction in squeal and friction aswell as improvement in fuel economy.

U.S. Pat. No. 4,952,328 discloses lubricating oil compositions forinternal combustion engines, comprising (A) oil of lubricatingviscosity, (B) a carboxylic derivative produced by reacting a succinicacylating agent with certain amines, and (C) a basic alkali metal saltof sulphonic or carboxylic acid.

U.S. Pat. No. 4,326,972 discloses lubricant compositions for improvingfuel economy of internal combustion engines. The composition includes aspecific sulphurised composition (based on an ester of a carboxylicacid) and a basic alkali metal sulphonate.

U.S. Patent Application 60/867,534 discloses malonate esters suitable asantiwear agents.

Canadian Patent CA 1 183 125 discloses lubricants for gasoline enginescontaining alkyl-ester tartrates, where the sum of carbon atoms on thealkyl groups is at least 8.

Consequently, it would be desirable to provide a lubricating compositioncapable of providing at least one of (i) reducing or preventingphosphorus emissions, (ii) reducing or preventing sulphur emissions,(ii) wholly or partially replacing ZDDP in lubricating oils, (iii)improving fuel economy, (iv) fuel economy retention/efficiency, and (v)oxidation control. The present invention provides an antiwear agentcapable of achieving at least one of (i), (ii) (iii), (iv), and (v). Inaddition it may also be desirable for the antiwear agent to not have adetrimental affect on other components of a mechanical device. It mayalso be desirable for the antiwear agent to have antioxidantperformance.

SUMMARY OF THE INVENTION

In one embodiment the invention provides a lubricating compositioncomprising an oil of lubricating viscosity, an oil-soluble molybdenumcompound, and an ashless antiwear agent represented by Formula (1):

wherein

Y and Y′ are independently —O—, >NH, >NR³, or an imide group formed bytaking together both Y and Y′ groups and forming a R¹—N<group betweentwo >C═O groups;

X is independently —Z—O—Z′—, >CH₂, >CHR⁴, >CR⁴R⁵, >C(OH)(CO₂R²),>C(CO₂R²)₂, >CCH₂CO₃R², or >CHOR⁶;

Z and Z′ are independently >CH₂, >CHR⁴, >CR⁴R⁵, >C(OH)(CO₂R²), or>CHOR⁶;

n is 0 to 10, or 1 to 8, or 1 to 6, or 2 to 6, or 2 to 4, with theproviso that when n=1, X is not >CH₂, and when n=2, both X′s are notsimultaneously >CH₂;

m is 0 or 1;

R¹ is independently hydrogen or a hydrocarbyl group, typicallycontaining 1 to 150, 4 to 30, or 6 to 20, or 10 to 20, or 11 to 18, or 8to 10 carbon atoms, with the proviso that when R¹ is hydrogen, m is 0,and n is more than or equal to 1;

R² is a hydrocarbyl group, typically containing 1 to 150, 4 to 30, or 6to 20, or 10 to 20, or 11 to 18, or 8 to 10 carbon atoms;

R³, R⁴ and R⁵ are independently hydrocarbyl groups or hydroxy-containinghydrocarbyl groups or carboxyl-containing hydrocarbyl groups; and

R⁶ is hydrogen or a hydrocarbyl group, typically containing 1 to 150, or4 to 30 carbon atoms.

In one embodiment the lubricating composition is characterised as havingat least one of (i) a sulphur content of 0.8 wt % or less, (ii) aphosphorus content of 0.2 wt % or less, or (iii) a sulphated ash contentof 2 wt % or less.

In one embodiment the invention the lubricating composition ischaracterised as having (i) a sulphur content of 0.5 wt % or less, (ii)a phosphorus content of 0.1 wt % or less, and (iii) a sulphated ashcontent of 1.5 wt % or less.

In one embodiment the invention provides a method of lubricating aninternal combustion engine comprising, supplying to the internalcombustion engine a lubricating compositions as disclosed herein.

In one embodiment the invention provides for the use of a lubricatingcomposition as disclosed herein for providing at least one of (i)reducing or preventing phosphorus emissions, (ii) reducing or preventingsulphur emissions, (ii) wholly or partially replacing ZDDP inlubricating oils, (iii) improving fuel economy, and (iv) fuel economyretention/efficiency.

In one embodiment the invention provides for the use of a compound ofFormula (1) as an antioxidant in a lubricant, wherein the compound ofFormula (1) may be represented by:

wherein

Y and Y′ are independently —O—, >NH, >NR³, or an imide group formed bytaking together both Y and Y′ groups and forming a R¹—N<group betweentwo >C═O groups;

X is independently —Z—O—Z′—, >CH₂, >CHR⁴, >CR⁴R⁵, >C(OH)(CO₂R²),>C(CO₂R²)₂, or >CHOR⁶;

Z and Z′ are independently >CH₂, >CHR⁴, >CR⁴R⁵, >C(OH)(CO₂R²), or>CHOR⁶;

n is 0 to 10, or 1 to 8, or 1 to 6, or 2 to 6, or 2 to 4, with theproviso that when n=1, X is not >CH₂, and when n=2, both X′s are not>CH₂;

m is 0 or 1;

R¹ is independently hydrogen or a hydrocarbyl group, typicallycontaining 1 to 150, 4 to 30, or 6 to 20, or 10 to 20, or 11 to 18, or 8to 10 carbon atoms, with the proviso that when R¹ is hydrogen, m is 0,and n is more than or equal to 1;

R² is a hydrocarbyl group, typically containing 1 to 150, 4 to 30, or 6to 20, or 10 to 20, or 11 to 18, or 8 to 10 carbon atoms;

R³, R⁴ and R⁵ are independently hydrocarbyl groups; and

R⁶ is hydrogen or a hydrocarbyl group, typically containing 1 to 150, or4 to 30 carbon atoms.

In one embodiment the invention provides for the use of the compound ofFormula (1) as an antioxidant in a lubricant, wherein the compound ofFormula (1) is an ester (such as a monoester, a diester or a triester).

In one embodiment the invention provides for the use of the compound ofFormula (1) as an antioxidant in a lubricant, wherein the compound ofFormula (1) is not a citrate.

In one embodiment the invention provides for the use of a tartaric acidderivative (typically a tartrate ester) as an antioxidant in alubricant.

In one embodiment the invention provides for the use of the compound ofFormula (1) (typically a tartaric acid derivative) as an antioxidant inan internal combustion engine lubricant.

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides a lubricating composition and a methodfor lubricating an engine as disclosed above.

Oil-Soluble Molybdenum Compound)

The oil-soluble molybdenum compound may have the functional performanceof an antiwear agent, an antioxidant, a friction modifier, or mixturesthereof. Typically, the oil-soluble molybdenum compound includesmolybdenum dithiocarbamates, molybdenum dialkyldithiophosphates, aminesalts of molybdenum compounds, molybdenum xanthates, molybdenumsulphides, molybdenum carboxylates, molybdenum alkoxides, or mixturesthereof. The molybdenum sulphides include molybdenum disulphide. Themolybdenum disulphide may be in the form of stable dispersions. In oneembodiment the oil-soluble molybdenum compound may be selected from thegroup consisting of molybdenum dithiocarbamates, molybdenumdialkyldithiophosphates, amine salts of molybdenum compounds, andmixtures thereof. In one embodiment the oil-soluble molybdenum compoundis a molybdenum dithiocarbamate.

Suitable examples of molybdenum dithiocarbamates which may be used as anantioxidant include commercial materials sold under the trade names suchas Molyvan 822™ and Molyvan™ A from R. T. Vanderbilt Co., Ltd., andAdeka Sakura-Lube™ S-100, S-165, S-515, and S-600 from Asahi Denka KogyoK.K and mixtures thereof.

The oil-soluble molybdenum compound may be present in an amountsufficient to provide 0.5 ppm to 2000 ppm, 1 ppm to 700 ppm, 1 ppm to550 ppm, 5 ppm to 300 ppm, or 20 ppm to 250 ppm of molybdenum.

Ashless Antiwear Agent

In one embodiment the compound of Formula (1) is an ashless antiwearagent, and it may also act as an antioxidant.

In one embodiment the compound of Formula (1) contains an imide group.The imide group is typically formed by taking together the Y and Y′groups and forming a R¹—N<group between two >C═O groups.

In one embodiment the compound of Formula (1) has m, n, X, and R¹, R²and R⁶ defined as follows: m is 0 or 1, n is 1 to 2, X is >CHOR⁶, andR¹, R² and R⁶ are independently hydrocarbyl groups containing 4 to 30carbon atoms.

In one embodiment Y and Y′ are both —O—.

In one embodiment the compound of Formula (1) has m, n, X, Y, Y′ and R¹,R² and R⁶ defined as follows: m is 0 or 1, n is 1 to 2, X is >CHOR⁶; Yand Y′ are both —O—, and R¹, R² and R⁶ are independently hydrogen orhydrocarbyl groups containing 4 to 30 carbon atoms.

In one embodiment the ashless antiwear agent includes imides, di-esters,di-amides, di-imides, ester-amides, ester-imides, or imide-amides. Inone embodiment the antiwear agent includes imides, di-esters, di-amides,or ester-amides.

The di-esters, di-amides, ester-amide, ester-imide compounds of Formula(1) may be prepared by reacting a dicarboxylic acid (such as tartaricacid), with an amine or alcohol, optionally in the presence of a knownesterification catalyst. In the case of ester-imide compounds it isnecessary to have at least three carboxylic acid groups (such as citricacid). In the case of a di-imide, it is necessary to have at least fourcarboxylic acid groups. The amine or alcohol typically has sufficientcarbon atoms to fulfill the requirements of R¹ and/or R² as defined inFormula (1).

In one embodiment R¹ and R² are independently linear or branchedhydrocarbyl groups. In one embodiment the hydrocarbyl groups arebranched. In one embodiment the hydrocarbyl groups are linear. The R¹and R² may be incorporated into Formula (1) by either an amine or analcohol. The alcohol includes both monohydric alcohol and polyhydricalcohol. The carbon atoms of the alcohol may be linear chains, branchedchains, or mixtures thereof.

Examples of a suitable branched alcohol include 2-ethylhexanol,isotridecanol, Guerbet alcohols, or mixtures thereof.

Examples of a monohydric alcohol include methanol, ethanol, propanol,butanol, pentanol, hexanol, heptanol, octanol, nonanol, decanol,undecanol, dodecanol, tridecanol, tetradecanol, pentadecanol,hexadecanol, heptadecanol, octadecanol, nonadecanol, eicosanol, ormixtures thereof. In one embodiment the monohydric alcohol contains 5 to20 carbon atoms.

The alcohol includes either a monohydric alcohol or a polyhydricalcohol. Examples of a suitable polyhydric alcohol include ethyleneglycol, propylene glycol, 1,3-butylene glycol, 2,3-butylene glycol,1,5-pentane diol, 1,6-hexane diol, glycerol, sorbitol, pentaerythritol,trimethylolpropane, starch, glucose, sucrose, methylglucoside, ormixtures thereof. In one embodiment the polyhydric alcohol is used in amixture along with a monohydric alcohol. Typically, in such acombination the monohydric alcohol constitutes at least 60 mole percent,or at least 90 mole percent of the mixture.

In one embodiment ashless antiwear agent is derived from tartaric acid.The tartaric acid used for preparing the tartrates of the invention canbe commercially available, and it is likely to exist in one or moreisomeric forms such as d-tartaric acid, l-tartaric acid or mesotartaricacid, often depending on the source (natural) or method of synthesis(from maleic acid). For example a racemic mixture of d-tartaric acid andl-tartaric acid is obtained from a catalysed oxidation of maleic acidwith hydrogen peroxide (with tungstic acid catalyst). These derivativescan also be prepared from functional equivalents to the diacid readilyapparent to those skilled in the art, such as esters, acid chlorides, oranhydrides.

When the compound of Formula (1) is derived from tartaric acid,resultant tartrates may be solid, semi-solid, or oil depending on theparticular alcohol used in preparing the tartrate. For use as additivesin a lubricating composition the tartrates are advantageously solubleand/or stably dispersible in such oleaginous compositions. For example,compositions intended for use in oils are typically oil-soluble and/orstably dispersible in an oil in which they are to be used. The term“oil-soluble” as used in this specification and appended claims does notnecessarily mean that all the compositions in question are miscible orsoluble in all proportions in all oils. Rather, it is intended to meanthat the composition is soluble in an oil (mineral, synthetic, etc.) inwhich it is intended to function to an extent which permits the solutionto exhibit one or more of the desired properties. Similarly, it is notnecessary that such “solutions” be true solutions in the strict physicalor chemical sense. They may instead be micro-emulsions or colloidaldispersions which, for the purpose of this invention, exhibit propertiessufficiently close to those of true solutions to be, for practicalpurposes, interchangeable with them within the context of thisinvention.

In one embodiment the ashless antiwear agent includes a compound derivedfrom a hydroxycarboxylic acid. In one embodiment the ashless antiwearagent is derived from at least one of hydroxy-polycarboxylic aciddi-ester, a hydroxy-polycarboxylic acid di-amide, ahydroxy-polycarboxylic acid di-imide, a hydroxy-polycarboxylic acidester-amide, a hydroxy-polycarboxylic acid ester-imide, and ahydroxy-polycarboxylic acid imide-amide. In one embodiment the ashlessantiwear agent is derived from at least one of the group consisting of ahydroxy-polycarboxylic acid di-ester, a hydroxy-polycarboxylic aciddi-amide, and a hydroxy-polycarboxylic acid ester-amide.

Examples of a suitable a hydroxycarboxylic acid include citric acid,tartaric acid, lactic acid, glycolic acid, hydroxy-propionic acid,hydroxyglutaric acid, or mixtures thereof. In one embodiment ashlessantiwear agent is derived from tartaric acid, citric acid,hydroxy-succinic acid, dihydroxy mono-acids, mono-hydroxy diacids, ormixtures thereof. In one embodiment the ashless antiwear agent includesa compound derived from tartaric acid or citric acid. In one embodimentthe ashless antiwear agent includes a compound derived from tartaricacid. In one embodiment the compound of Formula (1) is not a citrate.

US Patent Application 2005/198894 discloses suitable hydroxycarboxylicacid compounds, and methods of preparing the same.

Canadian Patent 1183125; US Patent Publication numbers 2006/0183647 andUS-2006-0079413; U.S. Patent Application No. 60/867,402; and BritishPatent 2 105 743 A, all disclose examples of suitable tartaric acidderivatives.

In one embodiment the di-esters, di-amides, di-imides, ester-amide,ester-imide, imide-amide compounds are derived from a compound ofFormula (1). In one embodiment the di-esters, di-amides, ester-amide,compounds are derived from a compound of Formula (1).

A detailed description of methods for preparing suitable tartrimides (byreacting tartaric acid with a primary amine) is disclosed in U.S. Pat.No. 4,237,022.

In one embodiment the ashless antiwear agent includes imide, di-esters,di-amides, ester-amide derivatives of tartaric acid.

Examples of a suitable citric acid derivative include trialkyl citratesor borated trialkyl citrates. Suitable examples include triethylcitrate, tripentyl citrate with ethyl dipentyl citrate, borated triethylcitrate, tributyl citrate, triethyl citrate transesterified with1,2-propandiol, triethyl O-acetyl citrate, triethyl citrate octadecylsuccinate, or mixtures thereof. A more detailed description of suitablecitrates is disclosed in WO 2005/087904 and U.S. Pat. No. 5,338,470.Other suitable citrates include 2-ethylhexyl citrate, dodecyl citrate,or mixtures thereof.

The ashless antiwear agent of the invention, typically a tartrate, mayalso function as rust and corrosion inhibitors, friction modifiers,antiwear agents and demulsifiers.

In one embodiment the ashless antiwear agent is not borated.

The ashless antiwear agent of the may be present at 0.01 wt % to 20 wt%, or 0.05 to 10 wt %, or 0.1 to 5 wt % of the lubricating composition.

Oils of Lubricating Viscosity

The lubricating composition comprises an oil of lubricating viscosity.Such oils include natural and synthetic oils, oil derived fromhydrocracking, hydrogenation, and hydrofinishing, unrefined, refined andre-refined oils and mixtures thereof.

Unrefined oils are those obtained directly from a natural or syntheticsource generally without (or with little) further purificationtreatment.

Refined oils are similar to the unrefined oils except they have beenfurther treated in one or more purification steps to improve one or moreproperties. Purification techniques are known in the art and includesolvent extraction, secondary distillation, acid or base extraction,filtration, percolation and the like.

Re-refined oils are also known as reclaimed or reprocessed oils, and areobtained by processes similar to those used to obtain refined oils andoften are additionally processed by techniques directed to removal ofspent additives and oil breakdown products.

Natural oils useful in making the inventive lubricants include animaloils, vegetable oils (e.g., castor oil,), mineral lubricating oils suchas liquid petroleum oils and solvent-treated or acid-treated minerallubricating oils of the paraffinic, naphthenic or mixedparaffinic-naphthenic types and oils derived from coal or shale ormixtures thereof.

Synthetic lubricating oils are useful and include hydrocarbon oils suchas polymerized, oligomerised, or interpolymerised olefins (e.g.,polybutylenes, polypropylenes, propyleneisobutylene copolymers);poly(1-hexenes), poly(1-octenes), timers or oligomers of 1-decene, e.g.,poly(1-decenes), such materials being often referred to as polyα-olefins, and mixtures thereof; alkyl-benzenes (e.g. dodecylbenzenes,tetradecylbenzenes, dinonylbenzenes, di-(2-ethylhexyl)-benzenes);polyphenyls (e.g., biphenyls, terphenyls, alkylated polyphenyls);diphenyl alkanes, alkylated diphenyl alkanes, alkylated diphenyl ethersand alkylated diphenyl sulphides and the derivatives, analogs andhomologs thereof or mixtures thereof.

Other synthetic lubricating oils include polyol esters (such asProlube®3970), diesters, liquid esters of phosphorus-containing acids(e.g., tricresyl phosphate, trioctyl phosphate, and the diethyl ester ofdecane phosphonic acid), or polymeric tetrahydrofurans. Synthetic oilsmay be produced by Fischer-Tropsch reactions and typically may behydroisomerised Fischer-Tropsch hydrocarbons or waxes. In one embodimentoils may be prepared by a Fischer-Tropsch gas-to-liquid syntheticprocedure as well as other gas-to-liquid oils.

Oils of lubricating viscosity may also be defined as specified in theAmerican Petroleum Institute (API) Base Oil InterchangeabilityGuidelines. The five base oil groups are as follows: Group I (sulphurcontent >0.03 wt %, and/or <90 wt % saturates, viscosity index 80-120);Group II (sulphur content ≦0.03 wt %, and ≧90 wt % saturates, viscosityindex 80-120); Group III (sulphur content ≦0.03 wt %, and ≧90 wt %saturates, viscosity index ≧120); Group IV (all polyalphaolefins(PAOs)); and Group V (all others not included in Groups I, II, III, orIV). The oil of lubricating viscosity comprises an API Group I, GroupII, Group III, Group IV, Group V oil or mixtures thereof. Often the oilof lubricating viscosity is an API Group I, Group II, Group III, GroupIV oil or mixtures thereof. Alternatively the oil of lubricatingviscosity is often an API Group II, Group III or Group IV oil ormixtures thereof.

The amount of the oil of lubricating viscosity present is typically thebalance remaining after subtracting from 100 wt % the sum of the amountof the ashless antiwear agent, the oil-soluble molybdenum compound andthe other performance additives.

The lubricating composition may be in the form of a concentrate and/or afully formulated lubricant. If the lubricating composition of theinvention (comprising (i) the ashless antiwear agent and (ii) theoil-soluble molybdenum compound) is in the form of a concentrate (whichmay be combined with additional oil to form, in whole or in part, afinished lubricant), the ratio of the of components of the invention tothe oil of lubricating viscosity and/or to diluent oil include theranges of 1:99 to 99:1 by weight, or 80:20 to 10:90 by weight.

Other Performance Additives

The composition optionally comprises other performance additives. Theother performance additives comprise at least one of metal deactivators,viscosity modifiers, detergents, friction modifiers (other than anoil-soluble molybdenum compound or a compound of Formula (1)), antiwearagents (other than the ashless antiwear agent of the invention),corrosion inhibitors, dispersants, dispersant viscosity modifiers,extreme pressure agents, antioxidants (other than an oil-solublemolybdenum compound of the invention), foam inhibitors, demulsifiers,pour point depressants, seal swelling agents and mixtures thereof.Typically, fully-formulated lubricating oil will contain one or more ofthese performance additives.

In one embodiment the lubricating composition comprises the ashlessantiwear agent and further comprises at least one of a viscositymodifier, an antioxidant, an overbased detergent, a succinimidedispersant, or mixtures thereof.

In one embodiment the lubricating composition comprising the ashlessantiwear agent further comprises a phosphorus-containing antiwear agent.

Detergents

The lubricant composition optionally further comprises other knownneutral or overbased detergents. Suitable detergent substrates includephenates, sulphur containing phenates, sulphonates, salixarates,salicylates, carboxylic acid, phosphorus acid, mono- and/ordi-thiophosphoric acid, alkyl phenol, sulphur coupled alkyl phenolcompounds, or saligenins. Various overbased detergents and their methodsof preparation are described in greater detail in numerous patentpublications, including WO2004/096957 and references cited therein. Thedetergent substrate is typically salted with a metal such as calcium,magnesium, potassium, sodium, or mixtures thereof. In one embodiment thelubricating composition further includes an overbased detergent.Typically the overbased detergent includes phenates, sulphur containingphenates, sulphonates, salixarates, salicylates, or mixtures thereof.

The detergent may be present at 0 wt % to 10 wt %, or 0.1 wt % to 8 wt%, or 1 wt % to 4 wt %, or greater than 4 to 8 wt %.

Dispersants

Dispersants are often known as ashless-type dispersants because, priorto mixing in a lubricating oil composition, they do not containash-forming metals and they do not normally contribute any ash formingmetals when added to a lubricant and polymeric dispersants. Ashless typedispersants are characterised by a polar group attached to a relativelyhigh molecular weight hydrocarbon chain. Typical ashless dispersantsinclude N-substituted long chain alkenyl succinimides. Examples ofN-substituted long chain alkenyl succinimides include polyisobutylenesuccinimide with number average molecular weight of the polyisobutylenesubstituent in the range 350 to 5000, or 500 to 3000. Succinimidedispersants and their preparation are disclosed, for instance in U.S.Pat. No. 3,172,892 or U.S. Pat. No. 4,234,435 or in EP 0355895.Succinimide dispersants are typically the imide formed from a polyamine,typically a poly(ethyleneamine).

In one embodiment the invention further comprises at least onepolyisobutylene succinimide dispersant derived from polyisobutylene withnumber average molecular weight in the range 350 to 5000, or 500 to3000. The polyisobutylene succinimide may be used alone or incombination with other dispersants.

In one embodiment the invention further comprises at least onedispersant derived from polyisobutylene succinic anhydride, an amine andzinc oxide to form a polyisobutylene succinimide complex with zinc. Thepolyisobutylene succinimide complex with zinc may be used alone or incombination.

Another class of ashless dispersant is Mannich bases. Mannichdispersants are the reaction products of alkyl phenols with aldehydes(especially formaldehyde) and amines (especially polyalkylenepolyamines). The alkyl group typically contains at least 30 carbonatoms.

The dispersants may also be post-treated by conventional methods by areaction with any of a variety of agents. Among these are boron, urea,thiourea, dimercaptothiadiazoles, carbon disulphide, aldehydes, ketones,carboxylic acids, hydrocarbon-substituted succinic anhydrides, maleicanhydride, nitriles, epoxides, and phosphorus compounds.

The dispersant may be present at 0 wt % to 20 wt %, or 0.1 wt % to 15 wt%, or 0.1 wt % to 10 wt %, or 1 wt % to 6 wt %, or 7 wt % to 12 wt % ofthe lubricating composition.

Antioxidants

Antioxidant compounds are known and include for example, sulphurisedolefins (typically sulphurised 4-carbobutoxy cyclohexane, ortriphenylphosphite equivalents thereof, or olefin sulphide), alkylateddiphenylamines (e.g., nonyl diphenylamine, typically di-nonyldiphenylamine, octyl diphenylamine, di-octyl diphenylamine), hinderedphenols, or mixtures thereof. Antioxidant compounds may be used alone orin combination. The antioxidant may be present in ranges 0 wt % to 20 wt%, or 0.1 wt % to 10 wt %, or 1 wt % to 5 wt %, of the lubricatingcomposition.

The hindered phenol antioxidant often contains a secondary butyl and/ora tertiary butyl group as a sterically hindering group. The phenol groupis often further substituted with a hydrocarbyl group and/or a bridginggroup linking to a second aromatic group. Examples of suitable hinderedphenol antioxidants include 2,6-di-tert-butylphenol,4-methyl-2,6-di-tert-butylphenol, 4-ethyl-2,6-di-tert-butylphenol,4-propyl-2,6-di-tert-butylphenol or 4-butyl-2,6-di-tert-butylphenol, or4-dodecyl-2,6-di-tert-butylphenol. In one embodiment the hindered phenolantioxidant is an ester and may include, e.g., Irganox™ L-135 from Cibaor an addition product derived from 2,6-di-tert-butylphenol and an alkylacrylate, wherein the alkyl group may contain 1 to 18, or 2 to 12, or 2to 8, or 2 to 6, or 4 carbon atoms. A more detailed description ofsuitable ester-containing hindered phenol antioxidant chemistry is foundin U.S. Pat. No. 6,559,105.

In one embodiment the lubricant does not contain (or contains reducedamounts of) phenolic antioxidant, when the compound of Formula (1) isemployed. This embodiment may be useful because the compound of Formula(1) may be used as a partial or whole replacement for phenolicantioxidants. It is believed that during the preparation of tertiarybutyl phenols trace amounts of an impurity tris-tert-butyl phenol areformed and retained in the final product. Tris-tert-butyl phenol isknown to bioaccumulate and builds up to high concentrations in sediment.Thus employing the compound of Formula (1) as an antioxidant may allowfor reduction of bioaccumulants.

Viscosity Modifiers

Viscosity modifiers include hydrogenated copolymers ofstyrene-butadiene, ethylene-propylene copolymers, polyisobutenes,hydrogenated styrene-isoprene polymers, hydrogenated isoprene polymers,polymethacrylates, polyacrylates, polyalkyl styrenes, hydrogenatedalkenyl aryl conjugated diene copolymers, polyolefins, esters of maleicanhydride-styrene copolymers, or esters of (alpha-olefin maleicanhydride) copolymers, or mixtures thereof.

Dispersant Viscosity Modifiers

Dispersant viscosity modifiers (often referred to as DVM), includefunctionalised polyolefins, for example, ethylene-propylene copolymersthat have been functionalised with the reaction product of an acylatingagent (such as maleic anhydride) and an amine; polymethacrylatesfunctionalised with an amine, or esterified maleic anhydride-styrenecopolymers reacted with an amine.

The total amount of viscosity modifier and/or dispersant viscositymodifier may be 0 wt % to 20 wt %, 0.1 wt % to 15 wt %, or 0.1 wt % to10 wt %, of the lubricating composition.

Antiwear Agents

The lubricant composition optionally further comprises at least oneother antiwear agent other than the ashless antiwear agent of theinvention. Examples of suitable antiwear agents include phosphateesters, sulphurised olefins, sulphur-containing anti-wear additivesincluding metal dihydrocarbyldithiophosphates (such as zincdialkyldithiophosphates), thiocarbamate-containing compounds including,thiocarbamate esters, alkylene-coupled thiocarbamates, andbis(S-alkyldithiocarbamyl) disulphides.

The dithiocarbamate-containing compounds may be prepared by reacting adithiocarbamate acid or salt with an unsaturated compound. Thedithiocarbamate containing compounds may also be prepared bysimultaneously reacting an amine, carbon disulphide and an unsaturatedcompound. Generally, the reaction occurs at a temperature of 25° C. to125° C. U.S. Pat. Nos. 4,758,362 and 4,997,969 describe dithiocarbamatecompounds and methods of making them.

Examples of suitable olefins that may be sulphurised to form an thesulphurised olefin include propylene, butylene, isobutylene, pentene,hexane, heptene, octane, nonene, decene, undecene, dodecene, undecyl,tridecene, tetradecene, pentadecene, hexadecene, heptadecene,octadecene, octadecenene, nonodecene, eicosene or mixtures thereof. Inone embodiment, hexadecene, heptadecene, octadecene, octadecenene,nonodecene, eicosene or mixtures thereof and their dimers, trimers andtetramers are especially useful olefins. Alternatively, the olefin maybe a Diels-Alder adduct of a diene such as 1,3-butadiene and anunsaturated ester, such as, butylacrylate.

Another class of sulphurised olefin includes fatty acids and theiresters. The fatty acids are often obtained from vegetable oil or animaloil and typically contain 4 to 22 carbon atoms. Examples of suitablefatty acids and their esters include triglycerides, oleic acid, linoleicacid, palmitoleic acid or mixtures thereof. Often, the fatty acids areobtained from lard oil, tall oil, peanut oil, soybean oil, cottonseedoil, sunflower seed oil or mixtures thereof. In one embodiment fattyacids and/or ester are mixed with olefins, such such as α-olefins.

In an alternative embodiment, the ashless antiwear agent (which may alsobe described as a friction modifier) may be a monoester of a polyol andan aliphatic carboxylic acid, often an acid containing 12 to 24 carbonatoms. Often the monoester of a polyol and an aliphatic carboxylic acidis in the form of a mixture with a sunflower oil or the like, which maybe present in the ashless antiwear agent mixture include 5 to 95, or inother embodiments 10 to 90, or 20 to 85, or 20 to 80 weight percent ofsaid mixture. The aliphatic carboxylic acids (especially amonocarboxylic acid) which form the esters are those acids typicallycontaining 12 to 24 or 14 to 20 carbon atoms. Examples of carboxylicacids include dodecanoic acid, stearic acid, lauric acid, behenic acid,and oleic acid.

Polyols include diols, triols, and alcohols with higher numbers ofalcoholic OH groups. Polyhydric alcohols include ethylene glycols,including di-, tri- and tetraethylene glycols; propylene glycols,including di-, tri- and tetrapropylene glycols; glycerol; butanediol;hexanediol; sorbitol; arabitol; mannitol; sucrose; fructose; glucose;cyclohexane diol; erythritol; and pentaerythritols, including di- andtripentaerythritol. Often the polyol is diethyl-ene glycol, triethyleneglycol, glycerol, sorbitol, pentaerythritol or dipentaerythritol. Thecommercial material known as glycerol monooleate is believed to includeabout 60±5 percent by weight of the chemical species “glycerolmonooleate,” along with 35±5 percent glycerol dioleate, and less thanabout 5 percent trioleate and oleic acid. The amounts of the monoesters,described below, are the amounts of the commercial grade material.

The antiwear agent may be present in ranges including 0 wt % to 15 wt %,or 0 wt % to 10 wt %, or 0.05 wt % to 5 wt %, or 0.1 wt % to 3 wt % ofthe lubricating composition.

In one embodiment the lubricating composition is free of zincdihydrocarbyl dithiophosphate. In one embodiment the lubricatingcomposition further includes zinc dihydrocarbyl dithiophosphate.

Extreme Pressure Agents

Extreme Pressure (EP) agents that are soluble in the oil includesulphur- and chlorosulphur-containing EP agents, chlorinated hydrocarbonEP agents and phosphorus EP agents. Examples of such EP agents includechlorinated wax; organic sulphides and polysulphides such asdibenzyldisulphide, bis-(chlorobenzyl) disulphide, dibutyltetrasulphide, sulphurised methyl ester of oleic acid, sulphurisedalkylphenol, sulphurised dipentene, sulphurised terpene, and sulphurisedDiels-Alder adducts; phosphosulphurised hydrocarbons such as thereaction product of phosphorus sulphide with turpentine or methyloleate; phosphorus esters such as the dihydrocarbon and trihydrocarbonphosphites, e.g., dibutyl phosphite, diheptyl phosphite, dicyclohexylphosphite, pentylphenyl phosphite; dipentylphenyl phosphite, tridecylphosphite, distearyl phosphite and polypropylene substituted phenylphosphite; metal thiocarbamates such as zinc dioctyldithiocarbamate andbarium heptylphenol diacid; amine salts of alkyl and dialkylphosphoricacids, including, for example, the amine salt of the reaction product ofa dialkyldithiophosphoric acid with propylene oxide; and mixturesthereof.

Friction Modifiers

In one embodiment the further comprises a friction modifier, or mixturesthereof. Typically the friction modifier may be present in rangesincluding 0 wt % to 10 wt %, or 0.05 wt % to 8 wt %, or 0.1 wt % to 4 wt%.

Examples of suitable friction modifiers include long chain fatty acidderivatives of long chain fatty acid derivatives of amines, esters, orepoxides; fatty imidazolines (that is, long chain fatty amides, longchain fatty esters, long chain fatty epoxide derivatives, and long chainfatty imidazolines); and amine salts of alkylphosphoric acids.

Friction modifiers may also encompass materials such as sulphurisedfatty compounds and olefins, triglycerides (e.g. sunflower oil) ormonoester of a polyol and an aliphatic carboxylic acid (all thesefriction modifiers have been described as antioxidants or antiwearagents).

In one embodiment the friction modifier is a long chain fatty amide, along chain fatty ester, a long chain fatty epoxide derivatives, or along chain fatty imidazoline.

In one embodiment the friction modifier is a long chain fatty acid ester(previously described above as an ashless antiwear agent). In anotherembodiment the long chain fatty acid ester is a mono-ester and inanother embodiment the long chain fatty acid ester is a (tri)glyceride.

Other Additives

Other performance additives such as corrosion inhibitors include thosedescribed in paragraphs 5 to 8 of US Application US05/038319 (filed onOct. 25, 2004 McAtee and Boyer as named inventors), octylamineoctanoate, and condensation products of dodecenyl succinic acid oranhydride and a fatty acid such as oleic acid with a polyamine. In oneembodiment the corrosion inhibitors include the Synalox® corrosioninhibitor. The Synalox® corrosion inhibitor is typically a homopolymeror copolymer of propylene oxide. The Synalox® corrosion inhibitor isdescribed in more detail in a product brochure with Form No.118-01453-0702 AMS, published by The Dow Chemical Company. The productbrochure is entitled “SYNALOX Lubricants, High-Performance Polyglycolsfor Demanding Applications.”

Metal deactivators including derivatives of benzotriazoles (typicallytolyltriazole), dimercaptothiadiazole derivatives, 1,2,4-triazoles,benzimidazoles, 2-alkyldithiobenzimidazoles, or2-alkyldithiobenzothiazoles; foam inhibitors including copolymers ofethyl acrylate and 2-ethylhexylacrylate and optionally vinyl acetate;demulsifiers including trialkyl phosphates, polyethylene glycols,polyethylene oxides, polypropylene oxides and (ethylene oxide-propyleneoxide) polymers; pour point depressants including esters of maleicanhydride-styrene, polymethacrylates, polyacrylates or polyacrylamides.

INDUSTRIAL APPLICATION

The lubricating composition may be utilised in a range of surfacestypically found in mechanical devices, including aluminum-alloysurfaces. The mechanical devices include an internal combustion engine,a gearbox, an automatic transmission, a hydraulic or a turbine.Typically the lubricating composition may be an engine oil, a gear oil,an automatic transmission oil, a hydraulic fluid, a turbine oil, a metalworking fluid or a circulating oil. In one embodiment the mechanicaldevice is an internal combustion engine.

In one embodiment the internal combustion engine may be a diesel fuelledengine, a gasoline fuelled engine, a natural gas fuelled engine or amixed gasoline/alcohol fuelled engine. In one embodiment the internalcombustion engine may be a diesel fuelled engine and in anotherembodiment a gasoline fuelled engine.

The internal combustion engine may be a 2-stroke or 4-stroke engine.Suitable internal combustion engines include marine diesel engines,aviation piston engines, low-load diesel engines, and automobile andtruck engines.

In one embodiment the internal combustion engine contains components ofan aluminium-alloy. The aluminium-alloy includes aluminium silicates,aluminium oxides, or other ceramic materials. In one embodiment thealuminium-alloy is an aluminium-silicate surface. As used herein, theterm “aluminum alloy” is intended to be synonymous with “aluminiumcomposite” and to describe a component or surface comprising aluminiumand another component intermixed or reacted on a microscopic or nearlymicroscopic level, regardless of the detailed structure thereof. Thiswould include any conventional alloys with metals other than aluminiumas well as composite or alloy-like structures with non-metallic elementsor compounds such as with ceramic-like materials.

The lubricant composition for an internal combustion engine may besuitable for any engine lubricant irrespective of the sulphur,phosphorus or sulphated ash (ASTM D-874) content. The sulphur content ofthe engine oil lubricant may be 1 wt % or less, or 0.8 wt % or less, or0.5 wt % or less, or 0.3 wt % or less. In one embodiment the sulphurcontent may be in the range of 0.001 wt % to 0.5 wt %, or 0.01 wt % to0.3 wt %. The phosphorus content may be 0.2 wt % or less, or 0.1 wt % orless, or 0.085 wt % or less, or even 0.06 wt % or less, 0.055 wt % orless, or 0.05 wt % or less. In one embodiment the phosphorus content maybe 100 ppm to 1000 ppm, or 325 ppm to 700 ppm. The total sulphated ashcontent may be 2 wt % or less, or 1.5 wt % or less, or 1.1 wt % or less,or 1 wt % or less, or 0.8 wt % or less, or 0.5 wt % or less. In oneembodiment the sulphated ash content may be 0.05 wt % to 0.9 wt %, or0.1 wt % or 0.2 wt % to 0.45 wt %. In another embodiment the sulphurcontent is 0.4 wt % or less, the phosphorus content is 0.08 wt % orless, and the sulphated ash is 1 wt % or less. In yet another embodimentthe sulfur content is 0.3 wt % or less, the phosphorus content is 0.05wt % or less, and the sulphated ash is 0.8 wt % or less.

In one embodiment the lubricating composition is an engine oil,

wherein the lubricating composition is characterised as having (i) asulphur content of 0.5 wt % or less, (ii) a phosphorus content of 0.1 wt% or less, and (iii) a sulphated ash content of 1.5 wt % or less.

In one embodiment the lubricating composition is suitable for a 2-strokeor a 4-stroke marine diesel internal combustion engine. In oneembodiment the marine diesel combustion engine is a 2-stroke engine. Theashless antiwear agent of the invention may be added to a marine diesellubricating composition at 0.01 to 20 wt %, or 0.05 to 10 wt %, or 0.1to 5 wt %.

The following examples provide illustrations of the invention. Theseexamples are non-exhaustive and are not intended to limit the scope ofthe invention.

EXAMPLES

As used herein all of the quantities for dispersants, detergents andviscosity modifiers shown below include conventional amount of diluentoil Typically the diluent oil constitutes 20 wt % to 90 wt % of eachcomponent. For antiwear agents, corrosion inhibitors, antioxidants theamounts shown are on an actives basis i.e. excluding diluent oil becausethe components are typically not carried in diluent oil.

Example 1 (EX1)

A lubricating composition is prepared containing 1 wt % ofdi-2-ethylhexyl tartrate, 0.6 wt % of other antiwear agents, 7.9 wt % ofdispersants, 1.5 wt % of detergents, 3.6 wt % of antioxidants includingan effective amount of molybdenum dithiocarbamate, 6.1 wt % of viscositymodifier, 0.1 wt % of corrosion inhibitor, and 0.1 wt % of frictionmodifier. The lubricating composition has a sulphated ash content of 0.6wt %, a phosphorus content of about 570 ppm, and a sulphur content of0.17 wt %.

Example 2 (EX2)

A lubricating composition is prepared containing 1 wt % of aC₁₂₋₁₄-alkyl tartrate, 4.1 wt % of dispersants, 1.4 wt % of detergents,2.5 wt % of antioxidants including 0.7 wt % of molybdenumdithiocarbamate (commercially available as Sakuralube™515, manufacturedby Asahi Denka), 0.56 wt % of antiwear agents, 0.1 wt % of corrosioninhibitor, and 0.1 wt % of friction modifier. The lubricatingcomposition has a phosphorus content of about 560 ppm.

Comparative Example 1 (CE1)

is similar to Example 2 except the composition does not contain 0.7 wt %of molybdenum dithiocarbamate, nor 1 wt % of a C₁₂₋₁₄-alkyl tartrate.

Comparative Example 2 (CE2)

is similar to Example 2 except the composition does not contain 0.7 wt %of molybdenum dithiocarbamate.

Comparative Example 3 (CE3)

is similar to Example 2 except the composition does not contain 1 wt %of a C₁₂₋₁₄-alkyl tartrate.

10 g samples of the examples above are each treated with one volumepercent of cumene hydroperoxide. The samples (2 ml portions) are thenevaluated for wear performance in an isothermal temperature highfrequency reciprocating rig (HFRR) available from PCS Instruments. HFRRconditions for the evaluations are 500 g load, 75 minute duration, 1000micrometer stroke, 20 hertz frequency, and at 105° C. Wear scar inmicrometers and film formation as percent film thickness are thenmeasured with lower wear scar values and higher film formation valuesindicating improved wear performance. The results obtained are:

Tartrate Wear Scar Film Thickness Examples (μm) (%) EX2 169 95 CE1 358 1CE2 188 88 CE3 189 57

Overall the results indicate that the lubricating composition of theinvention is capable of providing at least one of (i) reducing orpreventing phosphorus emissions, (ii) reducing or preventing sulphuremissions, (ii) wholly or partially replacing ZDDP in lubricating oils,(iii) improving fuel economy, and (iv) fuel economyretention/efficiency.

Example 3 (EX3)

A lubricating composition is designed to meet Euro 4 and Euro 5 emissionstandards and containing 1 wt % of C₈₋₁₀ alkyl tartrate. The lubricatingcomposition has a phosphorus content of 900 ppm or less, 0.3 wt % orless of sulphur, and 0.9 wt % or less of sulphated ash.

Example 4 (EX4)

A lubricating composition is designed to meet Euro 4 and Euro 5 emissionstandards and containing 1 wt % of C₈₋₁₀ alkyl tartrate. The lubricatingcomposition has a phosphorus content of 500 ppm or less, 0.2 wt % orless of sulphur, and 0.5 wt % or less of sulphated ash.

Comparative Examples 4 (CE4) and 5 (CE5)

are lubricating composition similar to EX3 and EX4 respectively, exceptthe C₈₋₁₀ alkyl tartrate is not included.

An iron-catalysed bulk oxidation test is carried out on EX3, EX4, CE4and CE5. The test is run at 170° C., with an air flow of 10 litres perhour, and in the presence of 360 ppm of iron catalyst. Oxidation ismeasured by the monitoring the peak area increase of the CO stretch fromFT-IR. The results obtained for EX4 and CE5 indicate that the relativepeak area increases by 383 units for EX4. In contrast, the relative peakarea increases by 428 units for CE5. Thus using a compound within thedefinition of Formula (1) of the present invention reduces oxidation ofa lubricant (especially an internal combustion engine).

It is known that some of the materials described above may interact inthe final formulation, so that the components of the final formulationmay be different from those that are initially added. The productsformed thereby, including the products formed upon employing lubricantcomposition of the present invention in its intended use, may not besusceptible of easy description. Nevertheless, all such modificationsand reaction products are included within the scope of the presentinvention; the present invention encompasses lubricant compositionprepared by admixing the components described above.

Each of the documents referred to above is incorporated herein byreference. Except in the Examples, or where otherwise explicitlyindicated, all numerical quantities in this description specifyingamounts of materials, reaction conditions, molecular weights, number ofcarbon atoms, and the like, are to be understood as modified by the word“about.” Unless otherwise indicated, each chemical or compositionreferred to herein should be interpreted as being a commercial gradematerial which may contain the isomers, by-products, derivatives, andother such materials which are normally understood to be present in thecommercial grade. However, the amount of each chemical component ispresented exclusive of any solvent or diluent oil, which may becustomarily present in the commercial material, unless otherwiseindicated. It is to be understood that the upper and lower amount,range, and ratio limits set forth herein may be independently combined.Similarly, the ranges and amounts for each element of the invention maybe used together with ranges or amounts for any of the other elements.

As used herein, the term “hydrocarbyl substituent” or “hydrocarbylgroup” is used in its ordinary sense, which is well-known to thoseskilled in the art. Specifically, it refers to a group having a carbonatom directly attached to the remainder of the molecule and havingpredominantly hydrocarbon character. Examples of hydrocarbyl groupsinclude:

(i) hydrocarbon substituents, that is, aliphatic (e.g., alkyl oralkenyl), alicyclic (e.g., cyclo alkyl, cycloalkenyl) substituents, andaromatic-, aliphatic-, and alicyclic-substituted aromatic substituents,as well as cyclic substituents wherein the ring is completed throughanother portion of the molecule (e.g., two substituents together form aring);

(ii) substituted hydrocarbon substituents, that is, substituentscontaining non-hydrocarbon groups which, in the context of thisinvention, do not alter the predominantly hydrocarbon nature of thesubstituent (e.g., halo (especially chloro and fluoro), hydroxy, alkoxy,mercapto, alkylmercapto, nitro, nitroso, and sulphoxy);

(iii) hetero substituents, that is, substituents which, while having apredominantly hydrocarbon character, in the context of this invention,contain other than carbon in a ring or chain otherwise composed ofcarbon atoms.

Heteroatoms include sulphur, oxygen, nitrogen, and encompasssubstituents as pyridyl, furyl, thienyl and imidazolyl. In general, nomore than two, preferably no more than one, non-hydrocarbon substituentwill be present for every ten carbon atoms in the hydrocarbyl group;typically, there will be no non-hydrocarbon substituents in thehydrocarbyl group.

While the invention has been explained in relation to its preferredembodiments, it is to be understood that various modifications thereofwill become apparent to those skilled in the art upon reading thespecification. Therefore, it is to be understood that the inventiondisclosed herein is intended to cover such modifications as fall withinthe scope of the appended claims.

The antiwear agent described herein may be an oil-soluble derivative ofa molecule containing a first carboxy group and at least one additional—OH, —NHR, or ═O moiety separated from the carbon of said first carboxygroup by a chain of 2 or 3 atoms, where R is hydrogen or alkyl, e.g,C1-6 alkyl.

1. A lubricating composition comprising an oil of lubricating viscosity,an oil-soluble molybdenum compound, and an ashless antiwear agentrepresented by Formula (1):

wherein Y and Y′ are independently —O—, >NH, >NR³, or an imide groupformed by taking together both Y and Y′ groups and forming a R¹—N<groupbetween two >C═O groups; X is independently —Z—O—Z′—, >CHR⁴, >CR⁴R⁵,>C(OH)(CO₂R²), >C(CO₂R²)₂, >CCH₂CO₂R² or >CHOR⁶; Z and Z′ areindependently >CH₂, >CHR⁴, >CR⁴R⁵, >C(OH)(CO₂R²), or >CHOR⁶; n is 0 to10, with the proviso that when n=1, X is not >CH₂, and when n=2, both X′s are not simultaneously >CH₂; m is 0 or 1; R¹ is independently hydrogenor a hydrocarbyl group, typically containing 1 to 150 carbon atoms, withthe proviso that when R¹ is hydrogen, m is 0, and n is more than orequal to 1; R² is a hydrocarbyl group, typically containing 1 to 150carbon atoms; R³, R⁴ and R⁵ are independently hydrocarbyl groups orhydroxy-containing hydrocarbyl groups or carboxyl-containing hydrocarbylgroups; and R⁶ is hydrogen or a hydrocarbyl group, typically containing1 to 150 carbon atoms.
 2. The lubricating composition of claim 1,wherein the ashless antiwear agent of Formula (1) is derived from atleast one hydroxy-polycarboxylic acid.
 3. The lubricating composition ofclaim 1 wherein the ashless anti-wear agent comprises ahydroxy-polycarboxylic acid di-ester, a hydroxy-polycarboxylic aciddi-amide, a hydroxyl-polycarboxylic acid imide, a hydroxy-polycarboxylicacid di-imide, a hydroxy-polycarboxylic acid ester-amide, ahydroxy-polycarboxylic acid ester-imide, and a hydroxy-polycarboxylicacid imide-amide.
 4. The lubricating composition of claim 1, wherein theashless antiwear agent represented by Formula (1) is an imide, adi-ester, or a di-amide.
 5. The lubricating composition of claim 1,wherein Y and Y′ of Formula (1) are both —O—.
 6. The lubricatingcomposition of claim 1, wherein Formula (1) defines m as 0 or 1, n as 1to 2, X is >CHOR⁶, and R¹, R² and R⁶ are independently hydrogen orhydrocarbyl groups containing 4 to 30 carbon atoms.
 7. The lubricatingcomposition of claim 1 wherein the ashless antiwear agent is derivedfrom tartaric acid or citric acid.
 8. The lubricating composition ofclaim 1, wherein the ashless antiwear agent is present at 0.05 to 10 wt%, or 0.1 to 5 wt % of the lubricating composition.
 9. The lubricatingcomposition of claim 1, wherein the oil-soluble molybdenum compound isselected from at least one member of the group consisting of molybdenumdithiocarbamates, molybdenum dialkyldithiophosphates, amine salts ofmolybdenum compounds, molybdenum xanthates, molybdenum sulphides,molybdenum carboxylates, and molybdenum alkoxides.
 10. The lubricatingcomposition of claim 9, wherein the oil-soluble molybdenum compound isselected from at least one member of the group consisting of molybdenumdithiocarbamates, molybdenum dialkyldithiophosphates, and amine salts ofmolybdenum compounds.
 11. The lubricating composition of claim 10,wherein the oil-soluble molybdenum compound is a molybdenumdithiocarbamate.
 12. The lubricating composition of claim 1, wherein theoil-soluble molybdenum compound is present in an amount to provide 0.5ppm to 2000 ppm, 1 ppm to 700 ppm, or 20 ppm to 250 ppm of molybdenum.13. The lubricating composition of claim 1, wherein the lubricatingcomposition is further characterised as having at least one of (i) asulphur content of 0.8 wt % or less, (ii) a phosphorus content of 0.2 wt% or less, or (iii) a sulphated ash content of 2 wt % or less.
 14. Thelubricating composition of claim 1, wherein the lubricating compositionis characterised as having (i) a sulphur content of 0.5 wt % or less,(ii) a phosphorus content of 0.1 wt % or less, and (iii) a sulphated ashcontent of 1.5 wt % or less.
 15. The lubricating composition of claim 1further comprises at least one of a friction modifier (other than anoil-soluble molybdenum compound or a compound of Formula (1)), aviscosity modifier, an antioxidant (other than the oil-solublemolybdenum compound), an overbased detergent, a succinimide dispersant,or mixtures thereof.
 16. The lubricating composition of claim 15,wherein the friction modifier is selected from the group consisting oflong chain fatty amides, long chain fatty esters, long chain fattyepoxide derivatives, long chain fatty imidazolines, and amine salts ofalkylphosphoric acids.
 17. The lubricating composition of claim 1further comprising a phosphorus-containing antiwear agent.
 18. Thelubricating composition of claim 1 further comprising an overbaseddetergent.
 19. The lubricating composition of claim 18, wherein theoverbased detergent is selected from the group consisting ofnon-sulphur-containing phenates, sulphur-containing phenates,sulphonates, salixarates, salicylates, and mixtures thereof.
 20. Amethod of lubricating an internal combustion engine comprising,supplying to the internal combustion engine the lubricating compositionof claim
 1. 21-22. (canceled)